Heat exchanger

ABSTRACT

A fluid liquid/fluid gas heat exchanger includes a hollow housing through which one of the fluids flows and whose exterior is exposed to the other fluid. The housing rotates about one or more non-rotating tubes which form inlet and outlet openings.

BACKGROUND

The present invention relates to a heat exchanger for transferring heat between a first liquid fluid and a gaseous fluid such as, for example, ambient air, and more particularly to a heat exchanger which has a hollow housing through which one of the fluids flows and whose exterior is exposed to the other fluid.

Such heat exchangers are used as coolers in vehicles. For example, published German patent application DE10139315 describes a heat exchanger in an engine cooling circuit. In such heat exchangers the coolant flows through tubing in a fixed, thin-walled cooler. The cooler is normally a flat, slab-shaped body and includes openings through which ambient air is blown. The cooler separates the two media, air and coolant. In order to attain a good heat exchange there is an advantage in a high flow velocity of the two media, coolant and ambient air, a high heat conductivity of the cooler and a large surface area of the cooler. Since the heat exchange between a fluid and a fixed body, as a rule, is very much easier than the heat exchange between a gas and a fixed body, the latter determines the dimensions of the cooler required for the transfer of a given amount of heat. Ribs can be used to increase the surface area of the cooler. But, for agricultural applications in which the ambient air is highly contaminated, ribs can become contaminated very rapidly, Thus, reducing the transfer of heat.

A blower may be used to blow air through the heat exchanger. The heat transfer performance is determined primarily by the amount of air conveyed, the flow velocity and the temperature difference between the outer surface of the cooler and the ambient air. A pump may be used to convey the fluid through the heat exchanger.

The disadvantage of these heat exchangers is the requirement for a large surface area for the side of the heat exchanger that is in contact with the ambient air. This surface area is considerably larger than the surface area that is in contact with the fluid. As a result, the heat exchanger must be large. A considerable amount of energy is also required in order to convey the two fluids, particularly the ambient air, through the heat exchanger. Contamination is a considerable problem in an agricultural application. There is a high cost in components and configuration as a result of the requirement for a pump, a blower and a cooler.

SUMMARY

Accordingly, an object of this invention is to provide a heat exchanger which has small dimensions with a high heat transfer performance capability.

A further object of the invention is to provide such a heat exchanger which requires relatively little operating energy, contain few costly components and reduces the danger of contamination.

These and other objects are achieved by the present invention, wherein a heat exchanger exchanges heat between a liquid fluid and a gas fluid. The heat exchanger includes a rotating hollow housing through which one of fluids flows and whose exterior is exposed to the other fluid. Preferably, the fluid flowing through the hollow housing is preferably a liquid, the gas flows around the hollow housing. The high circumferential velocity which is possible with a rotating hollow housing produces high flow velocities along its outer or inner circumferential surface, and an effective heat exchange. Thus, the performance of the heat exchange can be increased with a reduced surface area and smaller unit size compared to common conventional heat exchangers. The danger of contamination is reduced since the contaminant particles are not deposited in narrow penetration channels, but are blown away. It is furthermore possible to combine the functions of cooler, pump and blower in a unit, resulting in a simple design in which separate drives for pump and blower are omitted and that require considerably less energy to operate.

Preferably, in order to provide a good heat transfer, the hollow housing consists of aluminum, for example, of cast aluminum. The hollow housing preferably includes an axial inlet opening and an axial outlet opening for fluid flowing through it, where one fluid is conducted into the hollow housing through a first axial tube and is conducted out through a second tube which is coaxially with respect to the first tube, thus forming an annular channel between the tubes. With such a coaxial unit, only a single seal and a one bearing are required. Fluid can be supplied through the inner tube and then drained out through the annular channel, although fluid may flow in the opposite direction.

Preferably, overflow ports in the inlet tube communicate fluid directly from the inlet opening to the outlet opening. Thus, the cross sectional areas of the inlet and the outlet are designed so that a part of the fluid flows directly from the inlet to the outlet and not through the interior of the hollow housing on the basis of differing flow velocities in the inlet and the outlet. Preferably, a section of the return line can be configured as an injector to reduce the diameter near the bearing and seal area, while maintaining the same volume flow in the outer cooling circuit.

An alternate embodiment includes a single undivided tube which extends axially through the hollow housing and forms inlet and outlet openings located outside the hollow housing. Radial ports are formed in the portion of the tube inside the hollow housing so that fluid can flow out of the tube, into the hollow housing and back into the tube.

Preferably, the hollow housing includes a closable filler opening in an outer surface through which the hollow housing can be filled and drained. An elastic membrane may be mounted in the interior of the hollow housing to separate a part of the volume enclosed by the hollow housing from the fluid. The membrane may be preloaded, for example, by a spring or by a pressurized gas to equalize volume changes of the fluid flowing through the hollow housing.

A pump impeller may be rigidly fastened to the interior of the rotating hollow housing, and bearings can support both the pump impeller and the hollow housing, so that no additional bearing support of the pump impeller is required. The pump impeller is used to convey the fluid through the hollow housing.

The hollow housing may be connected rigidly to an external blower impeller which rotates with the housing. A single bearing may support both the blower impeller and the hollow housing. The pump impeller conveys the gas which flows along the outside of the hollow housing.

Preferably, a non-rotating guide impeller or guide housing is provided inside or outside the hollow housing upstream or downstream of the pump impeller or the blower impeller. The guide impeller and the guide housing interact with the associated pump impeller or blower impeller in order to assure an optimum guidance of the fluid. If the guide impeller is located within the hollow housing it may be necessary to configure the hollow housing as a multiple piece component so that the hollow housing can be disassembled in order to make an installation of the guide impeller possible.

In order to increase the surface area available for heat exchange, projections and recesses are provided on a (preferably cylindrical) outer surface and/or on a (preferably cylindrical) inner surface of the hollow housing. Preferably, these projections are helical blades arranged at an angle with respect to the axis of rotation, so that they can help convey either of the fluids. A non-rotating guide impeller or guide housing may also be arranged upstream and/or downstream of the blades.

The hollow housing can be driven by drives such as, for example, spur gears, flat belts, toothed belts, V-belts, toothed V-belts or roller chains. It is also possible to drive the hollow housing electrically and, in particular, to connect it rigidly with the rotor of an electric motor. The electric motor and the housing can be supported by the same bearings.

Preferably, the hollow housing is connected to the rotor of an asynchronous motor and simultaneously forms a short circuit ring of the asynchronous motor. A collar formed onto the hollow housing may be used as short circuit cage for the asynchronous motor. The housing may be manufactured as a one-piece cast aluminum unit with the collar used as short circuit cage. A second short circuit ring can be poured simultaneously during this manufacturing process. The stator of the asynchronous motor is inserted into a housing of a material with high heat conductivity (for example, cast aluminum), where the housing is in good heat conducting contact with the fluid flowing through the hollow housing. The rotor of the motor is also cooled very well by the fluid flowing through the hollow housing. The asynchronous motor can be operated with a frequency converter at a variable speed, stopped completely and/or to be operated in the reverse direction.

The temperature of the first and/or second fluids can be sensed by temperature sensors at the inlet and the outlet. Temperature signals may be transmitted to a control unit which controls the rotational speed of the asynchronous motor and as a function of the temperature measurements.

Preferably, the hollow housing is configured as a one-piece component together with a pump impeller, blower impeller, or projections and recesses, impeller blades and the short circuit cage and the short circuit ring of an electric motor. This one-piece component can be manufactured by casting, die casting, pressure die casting, forging, sintering from a material with good heat conductivity such as aluminum, an aluminum alloy, copper, a copper alloy, zinc, a zinc alloy, glass-fiber or carbon fiber-reinforced plastic or ceramic.

The invention increases the velocity of fluid gas flow around the hollow housing because the hollow housing rotates about an axis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a first embodiment of a heat exchanger;

FIG. 2 is a side view of the hollow housing of a heat exchanger according to the invention;

FIG. 3 is a schematic cross-sectional view of a second embodiment of heat exchanger according to the invention;

FIG. 4 is a schematic cross-sectional view of a third embodiment of a heat exchanger according to the invention; and

FIG. 5 is a schematic cross-sectional view of a fourth embodiment of a heat exchanger according to the invention.

DETAILED DESCRIPTION

FIG. 1 shows a cylindrical hollow housing 10 which includes an inlet port 12 and an outlet port 14. The inlet port 12 is supported for rotation by bearings 16 on a non-rotating inlet tube 18 and is sealed by a seal 20 with respect to the inlet tube 18. The outlet port 14 is supported for rotation by bearings 22 on a non-rotating outlet tube 24 and is sealed by a seal 26 with respect to the outlet tube 24. Thus, the housing 10 is supported by bearings for rotation about the central axis 28.

Inlet tube 18 forms an axial inlet opening 30, through which coolant can enter into the housing 10. Outlet tube 24 forms an axial outlet opening 32, through which coolant can leave the housing 10.

The housing 10 is driven by an asynchronous motor 34. A short circuit cage 36 is formed onto the outlet side of the housing 10 concentric with the housing 10, and cage 36 engages the rotor 38 of the asynchronous motor 34. A portion of the housing 10 is used as short circuit ring 40. A further short circuit ring 42 is formed onto the short circuit cage 36. The housing 10, short circuit cage 36 and short circuit ring 42 consist of a single component of cast aluminum. The stator 44 of the asynchronous motor 34 is inserted into a housing 46 of cast aluminum. The housing 46 is rigidly connected to the outlet tube 24, which also consists of aluminum with good heat conductivity. By means of this configuration the components of the asynchronous motor are in good heat conducting contact with the fluid flowing through the housing 10 and are very well cooled by the fluid. The bearing 24 supports both the asynchronous motor 34 and the housing 10.

The asynchronous motor 34 is connected to a control unit (not shown), that permits the asynchronous motor 34 to operate with variable rotational speed. Temperature sensors (not shown) are arranged near the inlet opening 30 and the outlet opening 32 to detect the inlet temperature and the outlet temperature of the fluid flowing through the housing 10. Moreover, a temperature sensor (not shown) is located near the circumferential surface of the hollow housing, and detects the temperature of the ambient air flowing around the housing 10. The signals of the temperature sensors are detected by the control unit and are utilized to control the rotational speed of the housing 10.

The exterior surface of the housing 10 is exposed to a flow of surrounding ambient air which cools the fluid flowing through the housing 10. The cooling effect depends on the dimensions of the housing 10, particularly its wall thickness and its heat conducting characteristics. With a high circumferential velocity of the rotating housing 10 an effective heat exchange occurs at its outer surface with the surroundings. The heat exchange depends crucially on the size of the outer surface of the housing 10 that is exposed to the cooling air. Therefore, the outer circumferential surface of the housing 10 is provided with a multitude of projections 48 and intervening recesses 50, that are in good heat conducting contact with the housing 10 and preferably are integral with the housing 10. As shown in FIG. 2, the projections 48 are configured as blades which are inclined with respect to the axis of rotation 28 which simultaneously operate to convey the cooling air and increase the cooling effect.

Referring now to FIG. 3, a single undivided tube 52 extends axially through and is received by the housing 10. Tube 52 forms at one end an inlet 30 and at its other end an outlet 32. The tube 52 includes ports 54 near inlet 30 which communicates fluid out of the tube 52 into the housing 10. Tube 52 also includes ports 56 near outlet 32 for communicating fluid from housing 10 back into tube 52, as indicated by arrows. The central portion of the tube 52 located between the ports 54, 56 is closed by a barrier (not shown), or is restricted by a throttling restriction (not shown) in order to prevent a flow of fluid through tube 52. Bearings 16 and 22 and seals 20 and 22 are installed between the tube 52 and housing 10.

To increase the effective surface in the interior of the housing 10, a plurality of projections 58 and intervening recesses 60 are formed on the inner wall of the housing 10. Projections 58 are in good heat conducting contact with the housing 10, and are preferably integral with the housing 10. The projections 58 are configured as blades which are inclined to the rotation axis 28, so that they help convey the fluid.

A V-belt pulley 62 is fixed to the outlet port 14 for rotation with the housing 10. Pulley 62 may be used to drive the housing 10 in rotation. The bearing 22 supports the pulley 62 and the housing 10. Instead of pulley, the housing 10 could be driven by other elements, such as, for example, a gear, a flat belt pulley, a toothed belt pulley, a chain sprocket and the like.

A blower impeller 64 is fixed to the inlet port 12 for rotation with the housing 10, and blows a flow of air across the surface of the housing 10 in order to cool the housing 10. Thus, a separately driven blower or blower impeller is not required. The bearing 20 supports both the blower impeller 64 and the housing 10. Non-rotating, non-rotating guide housings 66, 68 are positioned upstream and downstream of the blower impeller 64 for guiding the flow of air. In many applications, a single guide housing ahead of or behind the blower impeller 64 may be sufficient.

Referring now to FIG. 4, a pump impeller 70 is fastened to and rotates with a central portion of an inner surface of the housing 10. The pump impeller 70 can be manufactured as a one-piece unit with the housing 10 in a pressure die casting process. The bearings 16 and 22 support both the pump impeller 70 and the housing 10. The pump impeller 70 conveys the fluid through the housing 10, so that a separate fluid pump is not required.

Non-rotating impeller fluid flow guides 72, 74 are positioned upstream and downstream of the pump impeller 70 and are mounted on tube 10. It may be sufficient to provide only one guide 72 ahead of the pump impeller 70 or only one guide 74 behind the pump impeller 70. The housing 10 may be configured as a multi-piece component to permit assembly of the guides 72, 74.

Referring now to FIG. 5, hollow housing 80 includes a port 82 on one side only that is concentric to the axis of rotation 81. Two non-rotating concentric tubes 84, 86 are mounted in port 82. Coolant is supplied through the interior 85 of inner tube 84 into the housing 80. Coolant flows out of housing 80 through an annular passage formed between tubes 84 and 86. The port 82 is supported by a bearing 88 on the outer tube 86 and is sealed by a seal 90 against the outer tube 86. Additional bearings and seals can be omitted.

The inner tube 84 includes radial overflow ports 92 which permit fluid to flow between the inlet and the outlet. Due to differing fluid flow velocities in the supply and the drainage, a portion of the fluid flows directly from the inlet through the overflow channels 92 into the annular outlet channel 87 and not into the interior of the housing 80. Moreover the ends of the outer tube 86 are flared in a conical shape and the bearings and seals are located on the reduced diameter portion of tube 86. The fluid pressure will be reduced as it exits out of flared end of tube 86 and this lower pressure helps draw fluid through radial ports 92.

A filler opening 94 and a stopper 96 is located in the upper outer surface of the housing 80, according to FIG. 5. The filler opening 94 is used to fill and drain the housing 80 and the entire cooling arrangement with coolant. When being filled, the housing 80 is rotated into a position in which the filler opening 94 opens generally upward. When being drained, the housing 80 is rotated until the filler opening 94 opens downwardly.

As also shown in FIG. 5, an elastic membrane 98 in the interior of the housing 80 separates the housing 80 into two separate chambers 99 and 101. Chamber 101 is not exposed to fluid within housing 80. The elastic membrane 98 is preloaded by a spring 100 which permits changes in the volume of the chambers 99 and 101 as a result of differing temperatures. Alternatively, or in addition to the spring 100, chamber 101 could also be filled with a gas.

While the present invention has been described in conjunction with a specific embodiment, it is understood that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, this invention is intended to embrace all such alternatives, modifications and variations which fall within the spirit and scope of the appended claims.

Assignment

The entire right, title and interest in and to this application and all subject matter disclosed and/or claimed therein, including any and all divisions, continuations, reissues, etc., thereof are, effective as of the date of execution of this application, assigned, transferred, sold and set over by the applicant(s) named herein to Deere & Company, a Delaware corporation having offices at Moline, Ill. 61265, U.S.A., together with all rights to file, and to claim priorities in connection with, corresponding patent applications in any and all foreign countries in the name of Deere & Company or otherwise. 

1. A heat exchanger for exchanging heat between a liquid fluid and a gas fluid, the heat exchanger having a hollow housing, one of the fluids flowing through the housing and the other fluid flowing over an exterior of the housing, characterized by: the housing rotating about an axis.
 2. The heat exchanger of claim 1, wherein: the housing includes an axial inlet opening and an axial outlet opening through which fluid flows.
 3. The heat exchanger of claim 2, wherein: the inlet opening is formed in a non-rotating inlet tube; the outlet opening is formed in a non-rotating outlet tube; and the housing is rotatably supported by and sealed with respect to the inlet and outlet tubes.
 4. The heat exchanger of claim 1, further comprising: a hollow tube extends axially through the housing, the tube having a cylindrical wall forming an inlet opening and an outlet opening both located outside the housing, and the tube having radial ports in a portion of the tube located within the housing, the fluid flowing out of the tube and into the tube through the ports.
 5. The heat exchanger of claim 1, further comprising: an inlet pipe having an inlet opening and an outlet pipe coaxial with the inlet pipe and having an outlet opening, fluid flowing into and out of the housing coaxially from one side of the housing though the inlet and outlet pipes.
 6. The heat exchanger of claim 5, wherein: one of the inlet and outlet pipes including an over-flow port through which a portion of the fluid can flow directly from the inlet opening to the outlet opening.
 7. The heat exchanger of claim 6, wherein: the outlet pipe has a flared end.
 8. The heat exchanger of claim 1, further comprising: a filler opening formed in an outer portion of the housing; and a cover for closing the filler opening.
 9. The heat exchanger of claim 1, wherein: an elastic membrane is mounted inside the housing, the membrane enclosing a volume through which the fluid flows; and a resilient member is coupled to the membrane.
 10. The heat exchanger of claim 1, wherein: a pump impeller is attached to an interior wall of the housing and rotates with the housing.
 11. The heat exchanger of claim 1, further comprising: a pump impeller coupled for rotation with the housing; and a non-rotating guide positioned adjacent to the impeller.
 12. The heat exchanger of claim 1, further comprising: a plurality of blades formed on a surface of the housing.
 13. The heat exchanger of claim 12, wherein: the blades which are inclined with respect to a rotation axis of the housing.
 14. The heat exchanger of claim 1, further comprising: a blower impeller coupled to the housing.
 15. The heat exchanger of claim 14, wherein: the housing and the blower impeller are rotatably supported by a common bearing.
 16. The heat exchanger of claim 1, further comprising: a drive unit for transmitting torque to the housing.
 17. The heat exchanger of claim 1, wherein: the housing is coupled to a rotor of a asynchronous motor.
 18. The heat exchanger of claim 17, wherein: a portion of the housing comprises a short circuit ring of the asynchronous motor, and the housing includes a collar which comprises a short circuit cage for the asynchronous motor.
 19. The heat exchanger of claim 17, wherein: the asynchronous motor includes a stator which is received by a heat conducting housing which is exposed to the flowing fluid.
 20. The heat exchanger of claim 16, wherein: the drive unit and the housing are rotatably supported by a bearing.
 21. The heat exchanger of claim 10, wherein: the housing and the pump impeller are configured as a one-piece unit.
 22. The heat exchanger of claim 14, wherein: the housing and the blower impeller are configured as a one-piece unit.
 23. The heat exchanger of claim 10, wherein: the housing and the pump impeller are configured as a one-piece unit.
 24. The heat exchanger of claim 18, wherein: the housing and the short circuit cage are configured as a one-piece unit.
 25. The heat exchanger of claim 18, wherein: the housing, the short circuit cage and the short circuit ring are configured as a one-piece unit. 